U.S. patent application number 16/022895 was filed with the patent office on 2018-10-25 for base station apparatus and terminal device.
The applicant listed for this patent is Sharp Kabushiki Kaisha. Invention is credited to Jungo GOTO, Yasuhiro HAMAGUCHI, Osamu NAKAMURA, Hiromichi TOMEBA, Shiro WAKAHARA.
Application Number | 20180310294 16/022895 |
Document ID | / |
Family ID | 55019385 |
Filed Date | 2018-10-25 |
United States Patent
Application |
20180310294 |
Kind Code |
A1 |
GOTO; Jungo ; et
al. |
October 25, 2018 |
BASE STATION APPARATUS AND TERMINAL DEVICE
Abstract
In an LTE-A system, there is a problem that it is difficult to
perform stable communication in a case where there is a time when
another system occupies an unlicensed band being used. There is
provided a base station apparatus that communicates with a terminal
device in a second frequency band different from a first frequency
band capable of being used as a dedicated frequency band. The base
station apparatus includes: a wireless transmission unit that
transmits data or control information to the terminal device; and a
wireless reception unit that receives data or control information
transmitted from the terminal device. The wireless transmission
unit transmits data to the terminal device, and the wireless
reception unit performs a process of receiving ACK/NACK transmitted
from the terminal device in a subframe of an initial uplink after
communication of another system is ended in a case where the other
system performs the communication in the second frequency band at a
reception timing of the ACK/NACK of the data transmission.
Inventors: |
GOTO; Jungo; (Sakai City,
JP) ; NAKAMURA; Osamu; (Sakai City, JP) ;
TOMEBA; Hiromichi; (Sakai City, JP) ; WAKAHARA;
Shiro; (Sakai City, JP) ; HAMAGUCHI; Yasuhiro;
(Sakai City, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sharp Kabushiki Kaisha |
Sakai City |
|
JP |
|
|
Family ID: |
55019385 |
Appl. No.: |
16/022895 |
Filed: |
June 29, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15320326 |
Dec 20, 2016 |
|
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PCT/JP2015/069051 |
Jul 1, 2015 |
|
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16022895 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 1/1854 20130101;
H04W 16/14 20130101; H04L 5/0055 20130101; H04W 72/1215 20130101;
H04W 74/0808 20130101; H04J 11/00 20130101; H04W 72/0446 20130101;
H04L 1/1861 20130101; H04L 5/001 20130101; H04J 11/0073 20130101;
H04J 11/0076 20130101; H04W 72/0406 20130101; H04W 72/0453
20130101 |
International
Class: |
H04W 72/04 20090101
H04W072/04; H04W 16/14 20090101 H04W016/14; H04L 1/18 20060101
H04L001/18; H04J 11/00 20060101 H04J011/00; H04L 5/00 20060101
H04L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2014 |
JP |
2014-137378 |
Claims
1. A base station apparatus configured to communicate with a
terminal apparatus in a first frequency band and a second frequency
band, the second frequency band being an unlicensed frequency band,
the base station apparatus comprising: CS determination circuitry
configured to perform carrier sense in the second frequency band;
and wireless transmission circuitry configured to transmit a first
downlink signal and a second downlink signal, wherein the wireless
transmission circuitry transmits the first downlink signal in at
least a first slot on the first frequency band, and in a case where
the CS determination circuitry determines that communication is
idle in the second frequency band, the wireless transmission
circuitry transmits the second downlink signal on the second
frequency band for a period of time, the period of time being equal
to or less than a prescribed time, and transmits the second
downlink signal in a second slot on the second frequency band after
the carrier sense.
2. A terminal apparatus configured to communicate with a base
station apparatus in a first frequency band and a second frequency
band, the second frequency band being an unlicensed frequency band,
the terminal device comprising: reception signal detection
circuitry configured to receive a first downlink signal and a
second downlink signal, wherein the reception signal detection
circuitry detects the first downlink signal in at least a first
slot on the first frequency band, and in a case where the base
station device determines that, as a result of carrier sense,
communication is idle in the second frequency band, the reception
signal detection circuitry receives the second downlink signal on
the second frequency band for a period of time, the period of time
being equal to or less than a prescribed time, and detects the
second downlink signal in a second slot on the second frequency
band.
3. A communication method for a base station apparatus configured
to communicate with a terminal apparatus in a first frequency band
and a second frequency band, the second frequency band being an
unlicensed frequency band, the communication method comprising the
steps of: performing carrier sense in the second frequency band;
and transmitting a first downlink signal and a second downlink
signal, wherein transmitting the first downlink signal in at least
a first slot on the first frequency band, and in a case of
determining that communication is idle in the second frequency
band, transmiting the second downlink signal on the second
frequency band for a period of time, the period of time being equal
to or less than a prescribed time, and transmitting the second
downlink signal in a second slot on the second frequency band after
the carrier sense.
4. A communication method for a terminal apparatus configured to
communicate with a base station apparatus in a first frequency band
and a second frequency band, the second frequency band being an
unlicensed frequency band, the communication method comprising the
steps of: receiving a first downlink signal and a second downlink
signal, wherein detecting the first downlink signal in at least a
first slot on the first frequency band, and in a case of being
determined by the base station apparatus that, as a result of
carrier sense, communication is idle in the second frequency band,
receiving the second downlink signal on the second frequency band
for a period of time, the period of time being equal to or less
than a prescribed time, and detecting the second downlink signal in
a second slot on the second frequency band.
Description
TECHNICAL FIELD
[0001] The present invention relates to a base station apparatus
and a terminal device.
BACKGROUND ART
[0002] The standardization of a Long Term Evolution (LTE) system
which is a wireless communication system (Rel. 8 and Rel. 9) of
3.9G mobile phones has been completed, and the standardization of
LTE-Advanced (LTE-A) (also referred to as IMT-A) system (from Rel.
10 onwards) which is an enhancement of the LTE system as one of 4G
wireless communication systems has been currently performed.
[0003] The LTE system or the LTE-A system needs to cope with a
rapid increase in data traffic, and the introduction of a
technology for improving a peak data rate or spectral efficiency
and the reservation of frequency resources are important issues. In
the LTE system or the LTE-A system so far, the use of a frequency
band referred to as a so-called licensed band permitted for use
from a country or a locality in which a radio communication
operator provides services is assumed, and there are limitations of
an available frequency band.
[0004] Thus, the provision of the LTE system (referred to as LTE-U)
that uses a frequency band referred to as a so-called unlicensed
band which does not require the permission for use from country or
locality has been recently discussed (see NPL 1). In the LTE-A
system, a carrier aggregation (CA) technology which uses one system
band of the LTE system as a component carrier (CC) (also referred
to as a serving cell) and performs communication using a plurality
of CCs has been adopted. A method of applying this CA technology to
the unlicensed band and utilizing the unlicensed band has been
expected as one method for coping with the rapid increase in data
traffic.
[0005] It is considered that a frequency band (for example, a
frequency band which is allocated for television broadcasting but
is not used by the locality) called a white band (white space) that
is not used in reality in order to prevent the crosstalk between
frequencies or a shared frequency band which is exclusively
allocated to a specific operator but is expected to be shared
between a plurality of operators in the future is used for cellular
communication in the future in addition to the unlicensed band.
CITATION LIST
Non Patent Literature
[0006] NPL 1: RP-140259, "Study on Licensed-Assisted Access using
LTE," 3GPP TSG RAN Meeting #63, March 2014.
SUMMARY OF INVENTION
Technical Problem
[0007] However, as represented by an IEEE 802.11 system, since the
unlicensed band is also used for communication using a radio access
technology (RAT) different from LTE, the LTE-A system and another
system need to coexist. Particularly, since the use of the licensed
band is assumed in the LTE-A system of the related art, the LTE-A
system of the related art is not designed in consideration of a
case where a frequency band to be used may be occupied by another
system. Thus, in the LTE-A system, in a case where there is time
when another system occupies the unlicensed band being used, there
is a problem that stable communication is not able to be performed.
Even in a case where the LTE-A system uses a frequency band other
than the licensed band such as the white band (white space), there
is a possibility that the communication of the LTE-A system will be
influenced by another system similarly to a case where the
unlicensed band is used, and there is the same problem.
[0008] The present invention has been made in view of such
problems, and it is an object of the present invention to provide a
data transmission method capable of realizing stable communication
even though another system occupies an unlicensed band when an
LTE-A system uses the unlicensed band in a case where the LTE-A
system shares the unlicensed band or a white band with another
system.
Solution to Problem
[0009] (1) The present invention has been made in order to achieve
the aforementioned object, according to an aspect of the present
invention, there is provided a base station apparatus that
communicates with a terminal device in a second frequency band
different from a first frequency band capable of being used as a
dedicated frequency band. The base station apparatus includes: a
wireless transmission unit that transmits data or control
information to the terminal device; and a wireless reception unit
that receives data or control information transmitted from the
terminal device. The wireless transmission unit transmits data to
the terminal device, and the wireless reception unit performs a
process of receiving ACK/NACK transmitted from the terminal device
in a subframe of an initial uplink after communication of another
system is ended in a case where the other system performs the
communication in the second frequency band at a reception timing of
the ACK/NACK of the data transmission.
[0010] (2) According to the aspect of the present invention, the
wireless transmission unit transmits control information of
resource allocation for data transmission of the terminal device,
and the wireless reception unit performs a process of receiving
data transmitted from the terminal device in a subframe of an
initial uplink after communication of another system is ended in a
case where the other system performs the communication in the
second frequency band at a reception timing of data of the resource
allocation.
[0011] (3) According to another aspect of the present invention,
there is provided a base station apparatus that communicates with a
terminal device in a first frequency band capable of being used as
a dedicated frequency band and a second frequency band different
from the first frequency band. The base station apparatus includes:
a wireless transmission unit that transmits data or control
information to the terminal device; and a wireless reception unit
that receives data or control information transmitted from the
terminal device. The wireless transmission unit transmits data to
the terminal device, and the wireless reception unit performs a
process of receiving ACK/NACK transmitted from the terminal device
in the first frequency band in a case where another system performs
communication in the second frequency band at a reception timing of
ACK/NACK of the data transmission.
[0012] (4) According to the aspect of the present invention, the
wireless reception unit receives data transmitted from the terminal
device, and ACK/NACK is transmitted to the terminal device in the
first frequency band in a case where another system performs
communication in the second frequency band at a transmission timing
of ACK/NACK of the data transmission.
[0013] (5) According to the aspect, the base station apparatus
further includes: a data amount management unit that manages a
buffered data amount of a downlink. The wireless transmission unit
notifies of a NAV by using RTS or CTS-to-self or transmits dummy
data in a case where there is not the buffered data amount of the
downlink.
[0014] (6) According to still another system, there is provided a
terminal device that communicates with a base station apparatus in
a second frequency band different from a first frequency band
capable of being used as a dedicated frequency band. The terminal
device includes: an available subframe determination unit that
detects a synchronization signal transmitted from the base station
apparatus; a reception signal detection unit that performs a
process of receiving a data signal transmitted from the base
station apparatus; and a wireless transmission unit that transmits
a signal to the base station apparatus. In a case where ACK/NACK
indicating whether or not the data signal transmitted from the base
station apparatus is normally received by the reception signal
detection unit is transmitted, the wireless transmission unit
transmits the ACK/NACK in an uplink subframe after four subframes
from a timing when the data signal is received and after
notification indicating that another system does not perform
communication in the second frequency band is received by the
available subframe determination unit from the base station
apparatus.
[0015] (7) According to the aspect of the present invention, the
terminal device further includes: a control signal detection unit
that detects control information including resource allocation used
for data transmission to the base station apparatus. In a case
where the control signal detection unit detects control information
including resource allocation used for data transmission
transmitted from the base station apparatus, the wireless
transmission unit transmits data to the base station apparatus in
an uplink subframe after four subframes from a timing when the
resource allocation is received and after notification indicating
that another system does not perform communication in the second
frequency band is received from the base station apparatus.
[0016] (8) According to the aspect of the present invention, the
terminal device further includes: a wireless reception unit that
performs carrier sense for determining whether or not another
system performs communication in the second frequency band. The
wireless reception unit performs carrier sense in a subframe
switched from a downlink to an uplink.
[0017] (9) According to the aspect of the present invention, the
subframe switched to the uplink from the downlink in which the
wireless reception unit performs the carrier sense is a subframe
switched to an uplink from a downlink before a subframe in which
the ACK/NACK of downlink data or data transmitted to the base
station apparatus is transmitted.
[0018] (10) According to the aspect of the present invention, the
wireless reception unit performs carrier sense in only a frequency
band in which the ACK/NACK of downlink data or data transmitted to
the base station apparatus is transmitted.
[0019] (11) According to the aspect of the present invention, in a
case where the synchronization signal transmitted from the base
station apparatus is not able to be detected by the available
subframe determination unit or another system performs
communication in the second frequency band as a result of the
carrier sense of the wireless reception unit, the wireless
reception unit uses the first frequency band for the transmission
of the ACK/NACK of downlink data or data transmitted to the base
station apparatus.
Advantageous Effects of Invention
[0020] According to the present invention, it is possible to
efficiently share information indicating whether a base station
apparatus and a terminal device is able to use an unlicensed band
or is not able to use due to the reason why another system occupies
the unlicensed band.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a diagram showing an example of a structure of a
system according to the present invention.
[0022] FIG. 2 is a diagram showing a frame structure of TDD of an
LTE system.
[0023] FIG. 3 is a diagram showing an example of a frame structure
according to the present invention.
[0024] FIG. 4 is a diagram showing an example of a structure of a
base station apparatus according to the present invention.
[0025] FIG. 5 is a diagram showing an example of a structure of a
DL signal generation unit 101 according to the present
invention.
[0026] FIG. 6 is a diagram showing an example of a structure of a
terminal device according to the present invention.
[0027] FIG. 7 is a diagram showing an example of the frame
structure according to the present invention.
[0028] FIG. 8 is a diagram showing an example of a method of
multiplexing a synchronization signal according to the present
invention.
[0029] FIG. 9 is a diagram showing an example of the method of
multiplexing a synchronization signal according to the present
invention.
[0030] FIG. 10 is a diagram showing an example of transmission of
ACK/NACK of a downlink according to the present invention.
[0031] FIG. 11 is a diagram showing an example of the transmission
of ACK/NACK of the downlink according to the present invention.
[0032] FIG. 12 is a diagram showing an example of transmission of
ACK/NACK of an uplink according to the present invention.
[0033] FIG. 13 is a diagram showing an example of the transmission
of ACK/NACK of the uplink according to the present invention.
[0034] FIG. 14 is a diagram showing an example of the transmission
of ACK/NACK of the downlink according to the present invention.
[0035] FIG. 15 is a diagram showing an example of the transmission
of ACK/NACK of the downlink according to the present invention.
DESCRIPTION OF EMBODIMENTS
1. First Embodiment
[0036] Hereinafter, an embodiment will be described with reference
to the drawings. FIG. 1 illustrates an example of a structure of a
system according to the present invention. The system includes a
macro base station apparatus 10, a ULB base station apparatus 11,
and terminal devices 21 and 22. The number of terminal devices
(terminals, mobile terminals, mobile stations, or user equipment
(UE)) is not limited to 2, and the number of antennas of each
device may be 1, or may be plural in number. It is assumed that the
macro base station apparatus 10 performs communication using a
so-called licensed band of which permission for use is gained by a
country or a locality where a radio communication operator provides
services and the ULB base station apparatus 11 performs
communication using a so-called unlicensed band which does not
require the permission for use by the country or locality, but the
present invention is not limited to this example. For example, the
macro base station apparatus 10 may support the communication using
the unlicensed band as well as the licensed band, and a pico base
station apparatus (referred to as a pico eNB, Evolved Node B, small
cell, low power node, or remote radio head) capable of performing
the communication in the licensed band may support the
communication using the unlicensed band. The unlicensed band may
support only a downlink which is communication from the ULB base
station apparatus 11 to the terminal device 21, and may support an
uplink which is communication from the terminal device 21 to the
ULB base station apparatus 11 as well as the downlink. Although it
will be described in the present specification that a frequency
band other than the licensed band is the unlicensed band, the
present invention is not limited thereto.
[0037] The terminal device 21 may communicate with at least any one
of the macro base station apparatus 10 and the ULB base station
apparatus 11. Meanwhile, the terminal device 22 is connected to
only the macro base station apparatus 10. In such a case, the
terminal device 21 may communicate with any one CC or both CCs of a
component carrier (referred to as a CC or a serving cell) of the
licensed band and a CC of the unlicensed band. Here, in a case
where the CC (hereinafter, referred to as an ULB-CC) of the
unlicensed band is occupied by another system (for example,
802.11a, b, g, n, or ac), the terminal device 21 may perform
communication in only the CC (hereinafter, referred to as an LB-CC)
of the licensed band. In a case where the communication is
performed in the ULB-CC, at least one of the ULB base station
apparatus 11 and the terminal device 21 need to perform carrier
sense (for example, listen before talk) for checking whether or not
the ULB-CC is used by another system. For example, the ULB base
station apparatus 11 or the terminal device 21 may start
communication based on an access scheme called carrier sense
multiple access with collision avoidance (CSMA/CA). A specific
example of the carrier sense is to determine whether or not the
ULB-CC is used by another system depending on whether or not a
reception level (for example, a received signal strength indicator
(RSSI)) of a carrier frequency exceeds a threshold. Although it
will be described that time division duplex (referred to as TDD or
frame structure type 2) is applied to the ULB-CC, the ULB-CC may
support frequency division duplex (referred to as FDD or frame
structure type 1).
[0038] FIG. 2 illustrates a frame structure of the TDD of the LTE
system. In this drawing, in the TDD of the LTE system, a plurality
of uplink-downlink configurations is prepared, and is appropriately
configured on a per CC basis. D is a downlink subframe, U is an
uplink subframe, and S is a special subframe. The special subframe
includes a guard period (GP), a downlink pilot time slot (DwPTS),
and an uplink pilot time slot (UpPTS) which are required when from
the downlink to the uplink is switched. A cycle at which switching
is performed from the downlink to the uplink is 5 msec
(configurations #0, #1, #2, and #6) and 10 msec (configurations #3,
#4, and #5). A pattern of the D, U, and S used at this cycle is
repeated. Since an LTE system or an LTE-A system can occupy and use
the licensed band, this system constantly performs communication
with any pattern.
[0039] FIG. 3 illustrates an example of a frame structure according
to the present invention. In the ULB-CC of the unlicensed band, for
the coexistence with another system, since it is necessary to
perform the carrier sense (CS) before communication is started, the
subframe #0 and the subframe #5 which are C in this drawing are
periods during which the carrier sense is performed. In a case
where the ULB base station apparatus 11 performs the carrier sense
in at least the subframes #0 and #5 and another system does not use
the ULB-CC, the transmission of the downlink is started in the
subframe #1. In a case where the ULB base station apparatus 11
performs the carrier sense in the subframe #0 and #5 and another
system uses the ULB-CC, the transmission is not performed until it
is checked that another system does not use the ULB-CC in the
subframe of the carrier sense. Specifically, in a case where it is
determined that another system uses the ULB-CC as a result of the
carrier sense in the subframe #0, the ULB base station apparatus 11
regards the subframes #1 to #4 as unavailable subframes. That is,
the communication using the ULB-CC between the ULB base station
apparatus 11 and the terminal device is not performed in the
subframes #1 to #4. Meanwhile, in a case where it is determined
that another system does not use the ULB-CC as a result of the
carrier sense in the subframe #0, the ULB base station apparatus 11
regards the subframes #1 to #4 as available subframes. That is, the
communication using the ULB-CC between the ULB base station
apparatus 11 and the terminal device is performed in the subframes
#1 to #4.
[0040] FIG. 4 illustrates an example of a structure of the base
station apparatus according to the present invention. Here, minimum
blocks required in the present invention are illustrated. This
drawing is a structure example of the ULB base station apparatus
11, but the ULB base station apparatus has the same structure as
that of a base station apparatus (for example, a macro base station
apparatus 10) that performs communication in only the LB-CC of the
licensed band in that a CS determination unit 106 is not provided.
The ULB base station apparatus 11 receives control information
transmitted over physical uplink control channel (PUCCH) or control
information transmitted over physical uplink shared channel (PUSCH)
from the terminal device by the receive antenna 104. A reception
process for checking whether or not another system uses the ULB-CC
is performed in the subframe of the carrier sense. In the case of
the uplink subframe, a wireless reception unit 105 performs
up-conversion of the reception signal so as to convert a frequency
of the signal to a baseband frequency, converts analog/digital
(A/D) conversion, and inputs a signal acquired by removing cyclic
prefix (CP) from the digital signal to a UL signal demodulation
unit 107. Thereafter, the UL signal demodulation unit 107 extracts
channel state information (CSI), scheduling request (SR),
acknowledgement/negative acknowledgement (ACK/NACK), or a random
access channel (RACH) signal from the control information having no
CP, and inputs the extracted information to a DL signal generation
unit 101. The UL signal demodulation unit 107 demodulates a data
signal, and detects a data bit array of the uplink.
[0041] Meanwhile, in the case of the subframe of the carrier sense,
the wireless reception unit 105 inputs the reception signal to the
CS determination unit 106. The CS determination unit 106 determines
whether or not another system uses the ULB-CC as a result of the
carrier sense, determines to set the subframes including the next
subframe of the carrier sense to be the available subframes or the
unavailable subframes, and determines whether or not to perform the
communication using the ULB-CC. Even though another system does not
use the ULB-CC as a result of the carrier sense, the subframe of
the carrier sense may be set to be the unavailable subframe in a
case where there is no transmission data of the downlink. The CS
determination unit 106 inputs information indicating whether or not
the ULB-CC is able to be used to the DL signal generation unit
101.
[0042] FIG. 5 illustrates an example of a structure of the DL
signal generation unit 101 according to the present invention. The
DL signal generation unit 101 outputs the information indicating
whether or not the ULB-CC is able to be used which is input from a
CS determination unit 106 to the S/P unit 1011, a synchronization
signal generation unit 1016, a control signal generation unit 1017,
and a reference signal generation unit 1018. The DL signal
generation unit 101 outputs the control information of the uplink
input from the UL signal demodulation unit 107 to the S/P unit 1011
and the control signal generation unit 1017. In a case where the
ULB-CC is not able to be used (in a case where it is determined
that the subframe is the unavailable subframe), the S/P unit 1011,
the synchronization signal generation unit 1016, the control signal
generation unit 1017, and the reference signal generation unit 1018
do not perform any process. In a case where the ULB-CC is able to
be used (in a case where it is determined that the subframe is the
available subframe), these units perform the following process. The
S/P unit 1011 receives the ACK/NACK of the previous transmission
occasion from the UL signal demodulation unit 107, and divides a
new data bit array into a predetermined number of transmission
streams in a case where the ACK is input. The S/P unit 1011 divides
the data bit array transmitted on the previous transmission
occasion into a predetermined number of transmission streams in a
case where the NACK is input. Although it will be described in the
present embodiment that the number of streams is 2, the number of
streams may be plural in number, or may be 1. The data signal
generation units 1012-1 and 1012-2 generate a data transmit signal
sequence from the data bit array. Here, the processes of the data
signal generation units 1012-1 and 1012-2 include error correction
coding, puncturing and modulation based on a modulation and coding
scheme (MCS), signal generation for each antenna port through the
multiplication of a precoding matrix, and allocation of a signal
sequence to a resource used in the downlink based on resource
allocation information. It is assumed that the resource is a
resource block (RB) including 12 subcarriers or one subframe, or
resource block group (RBG) acquired by grouping a plurality of RBs.
Here, the number of subcarriers constituting the resource block is
not limited to the above-described example, and the resource may be
allocated on a per subcarrier basis using one resource block as one
subcarrier. The resource allocation information may indicate the
allocation of all the subcarriers included in one ULB-CC, or may be
information indicating an ULB-CC to be used in a case where there
is a plurality of ULB-CCs. The resource allocation information may
be information indicating the allocated subcarriers among all the
subcarriers of the plurality of ULB-CCs.
[0043] The synchronization signal generation unit 1016 generates
primary synchronization signal/secondary synchronization signal
(PSS/SSS), and inputs the generated signal to synchronization
signal multiplexing units 1013-1 and 1013-2. The synchronization
signal multiplexing units 1013-1 and 1013-2 multiplex the data
transmit signal sequence with the PSS/SSS. A method of multiplexing
the PSS/SSS in the present embodiment will be described below.
Subsequently, a signal, such as a physical downlink control channel
(PDCCH) or an enhanced PDCCH (EPDCCH) which is control signals
generated by the control signal generation unit 1017, which is
acquiring by multiplexing the synchronization signal with the data
transmit signal sequence, is multiplexed by control signal
multiplexing units 1014-1 and 1014-2. A downlink reference signal,
for example, a cell-specific reference signal (CRS), a channel
state information reference signal (CSI-RS), or a de-modulation
reference signal (DMRS), which is generated by the reference signal
generation unit 1018, is input to the reference signal multiplexing
units 1015-1 and 1015-2, and is multiplexed with outputs of control
signal multiplexing units 1014-1 and 1014-2. IFFT units 1019-1 and
1019-2 convert a frequency-domain signal sequence into a
time-domain signal sequence by performing inverse fast Fourier
transform (IFFT) on the signal sequence.
[0044] Wireless transmission units 102-1 and 102-2 insert the CP
into the time-domain signal sequence, convert the digital signal
into an analog signal by performing digital/analog (D/A), and
performs up-conversion of a converted signal so as to convert a
frequency of the converted signal into a radio frequency to be used
for transmission. The wireless transmission units 102-1 and 102-2
amplify the up-converted signal by a power amplifier (PA), and
transmit the amplified signal through transmit antennas 103-1 and
103-2. As stated above, in the downlink, an orthogonal frequency
division multiplexing signal (OFDM) is transmitted to the terminal
device.
[0045] FIG. 6 illustrates an example of a structure of the terminal
device according to the present invention. The signals are received
by receive antennas 201-1 and 201-2. Wireless reception units 202-1
and 202-2 perform down-conversion of the reception signal so as to
covert a frequency of the reception signal into a baseband
frequency, and generate a digital signal by performing A/D
conversion on the down-converted signal. The wireless reception
units 202-1 and 202-2 input a signal acquired by removing the CP
from the digital signal to an available subframe determination unit
210.
[0046] The available subframe determination unit 210 detects the
PSS/SSS at a reception timing of a signal which includes the
PSS/SSS to be described below. If the detection of the PSS/SSS
fails, the ULB base station apparatus 11 determines that the ULB-CC
is used by another system or there is no data signal to be
transmitted, and the terminal device regards the subframes
including the next subframe of the carrier sense as the unavailable
subframes. The terminal device does not perform a reception process
of downlink data or the control signal in the unavailable subframe.
For example, in the frame structure example of FIG. 3, in a case
where the detection of the PSS/SSS included in the SFNs #0 to #4
fails, the SFNs #0 to #4 of the ULB-CC are not used. Here, a case
where the detection of the PSS/SSS fails is a case where a received
power is less than a previously configured threshold or a
correlation value is less than a threshold. Subsequently, in a case
where the detection of the PSS/SSS succeeds, the terminal device
determines that the ULB-CC is used, and regards the subframes
including the next subframe of the carrier sense as the available
subframes. The terminal device performs a reception process of the
downlink or a transmission process of the uplink in the available
subframe. For example, in the frame structure example of FIG. 3, in
a case where the detection of the PSS/SSS included in the SFNs #0
to #4 succeeds, the SFNs #0 to #4 of the ULB-CC are used. At a
reception timing of the signal which does not include the PSS/SSS,
the available subframe determination unit 210 inputs the reception
signal to FFT units 203-1 and 203-2 in a case where the detection
of the PSS/SSS succeeds, and discards the reception signal in a
case where the detection of the PSS/SSS fails.
[0047] The FFT units 203-1 and 203-2 convert the time-domain signal
sequence into the frequency-domain signal sequence by performing
fast Fourier transform on the input reception signal sequence, and
input the frequency-domain signal sequence to control signal
demultiplexing units 205-1 and 205-2. The control signal
demultiplexing units 205-1 and 205-2 demultiplex the signal
transmitted over the PDCCH or the EPDCCH in the downlink subframe
of the available subframe, and input the demultiplexed signals to a
control signal detection unit 209. Even in a case where a radio
resource control (RRC) signal is received, the control signal
demultiplexing units 205-1 and 205-2 demultiplex the signal, and
inputs the demultiplexed signals to the control signal detection
unit 209. The control signal detection unit 209 detects a downlink
control information (DCI) format addressed to the terminal device
the over the PDCCH or the EPDCCH through blind decoding. The
control signal detection unit 209 detects the RRC signal. The
control signal detection unit 209 inputs the detected control
information to the reception signal detection unit 207.
[0048] Reference signal demultiplexing units 206-1 and 206-2
demultiplex the input signal into the reference signal and the data
signal, and inputs the demultiplexed signals to the channel
estimation unit 208 and the reception signal detection unit 207.
The channel estimation unit 208 estimates a frequency response of a
channel for demodulation by using the CRS, the CSI-RS, or the DMRS
which is the input reference signal, and inputs the estimated
frequency response for demodulation to the reception signal
detection unit 207. Although not illustrated, the channel
estimation unit 208 inputs the channel state information (CSI)
estimated using the CRS or the CSI-RS to an UL control information
generation unit 215 in order to periodically or aperiodically
notify (report) the base station apparatus of the information. The
reception signal detection unit 207 detects the data signal of the
downlink. The reception signal detection unit 207 performs an
equalization process based on the frequency response of the
channel, a demodulation process based on a modulation scheme
notified through the DCI format, and an error correction decoding
process of a log likelihood ratio (LLR) of a bit sequence acquired
through demodulation by using information of the error correction
coding notified through the DCI format. The reception signal
detection unit 207 performs hard decision on the decoded LLR
sequence, and outputs the bit array in a case where there is no
error through a cyclic redundancy check (CRC). The reception signal
detection unit 207 inputs information indicating whether or not
there is an error of the reception data to the UL control
information generation unit 215. This information is used for
transmitting the ACK/NACK.
[0049] Meanwhile, the available subframe determination unit 210
stores the detection result of the PSS/SSS and the frame structure
which is previously notified and is used in the ULB-CC. The frame
structure is notified using a control signal of a higher layer, and
is, for example, RRC signalling. Here, the frame structure may be
notified using a control signal of a physical layer. A frame
structure example used in the ULB-CC is an example described in
FIG. 7. In the example of this drawing, in structures #0 to #3, the
subframes in which the carrier sense is performed are repeated at
five subframe cycles, and in structures #4 to #9, the subframes in
which the carrier sense is performed are repeated at 10 subframe
cycles. The structure example of the frame used in the ULB-CC is
not limited to FIG. 7, and may include the subframes in which the
carrier sense is performed and the downlink subframes. For example,
a proportion between the downlink and uplink subframes or a cycle
of a subframe in which the carrier sense is performed may be
different from that in the structure described in FIG. 7.
[0050] In a case where information of the detection result of the
PSS/SSS indicates detection success, the available subframe
determination unit 210 inputs the notified information of the
information of the uplink subframe (information of the available
subframe of the uplink) to an UL signal generation unit 211 and the
UL control information generation unit 215. In a case where the
information of the detection result of the PSS/SSS indicates
detection success, the available subframe determination unit 210
inputs the notified information of the timing of the downlink
subframe (information of the available subframe of the downlink) to
the control signal demultiplexing units 205-1 and 205-2. In a case
where the information of the detection result of the PSS/SSS
indicates detection failure (it is determined that the subframe is
the unavailable subframe), the available subframe determination
unit 210 does not any process. The UL signal generation unit 211
converts the data signal of the uplink into discrete Fourier
transform spread OFDM (DFTS-OFDM: referred to as SC-FDMA). Although
the DFTS-OFDM is used in the present embodiment, the present
invention is not limited thereto, and a multi-carrier signal such
as OFDM or MC-CDMA may be used. The process performed by the UL
signal generation unit 211 includes error correction coding,
modulation, DFT, frequency resource allocation, and IFFT.
Information of the ACK/NACK is input to the UL control information
generation unit 215 from the reception signal detection unit 207,
and although not illustrated, the information of the CSI is input
thereto from the channel estimation unit 208. The UL control
information generation unit 215 converts the ACK/NACK or periodic
CSI into a format of uplink control information (UCI) transmitted
over the PUCCH, and inputs the converted information to an UL
control information multiplexing unit 212. The UL control
information multiplexing unit 212 multiplexes the uplink data with
the control information. Here, in a case where the PUSCH and the
PUCCH are not simultaneously transmitted, only one signal thereof
constitutes a transmission frame. In a case where a resource
allocation request of the uplink is performed, the UL control
information generation unit 215 generates the SR or the RACH
signal, and transmits the generated signal. Here, the SR is
transmitted over the PUCCH, and the RACH signal uses a
predetermined resource. The uplink signal is transmitted through
the wireless transmission unit 213 and the transmit antenna
214.
[0051] Although it has been described that the control signal of
the uplink is transmitted in the ULB-CC, the UL control information
generation unit 215 does not any process on the signal transmitted
to the ULB-CC in a case where the control signal of the uplink is
transmitted in only the LB-CC. Although it has been described that
the data signal of the uplink is transmitted in the ULB-CC, in a
case where the structure in which there is not the subframe of the
uplink is used (or configured) in TDD or the ULB-CC is only the CC
(serving cell) of the downlink in FDD, the UL signal generation
unit 211, the UL control information multiplexing unit 212, the UL
control information generation unit 215, the wireless transmission
unit 213, and the transmit antenna 214 are used in only at the time
of the transmission to the LB-CC.
[0052] Although the subframe structure is illustrated in FIGS. 3
and 7, each subframe includes a plurality of OFDM symbols, and 14
OFDM symbols constitute one subframe in the LTE system. Here, in
the present invention, the number of OFDM symbols of one subframe
is not limited, and an example of 14 OFDM symbols (symbols #0 to
#13) will be described. In the present invention, the number of
subframes of one frame is not limited, and an example of 10
subframes (subframes #0 to #9) will be described. In the LTE
system, the PSS is allocated to the third OFDM symbol (symbol #2)
of the subframes #1 and #6 and the SSS is allocated to the seventh
OFDM symbol (symbol #6) of the subframes #0 and #5 in TDD, and the
PSS is allocated to the last OFDM symbol (symbol #13) of the
subframes #0 and #5, and the SSS is allocated to the sixth OFDM
symbol (symbol #5) of the subframes #0 and #5 in FDD.
[0053] Here, in the ULB-CC, in a case where the frame structure
including the subframes of the carrier sense is applied before the
data transmission illustrated in FIG. 3 in TDD, it is necessary to
recognize the subframes in which the terminal device can perform
transmission or reception of data at an earlier timing. The PSS of
the LTE system of the related art is allocated to the first
subframe of the downlink of FIG. 3, but since the initial subframe
is the third OFDM symbol, the PSS is not allocated to the leading
OFDM symbol. The SSS of the LTE system of the related art is
allocated to the seventh OFDM symbol of the subframe of the carrier
sense of FIG. 3. Thus, it is not possible to efficiently recognize
the available subframe between the ULB base station apparatus and
the terminal device.
[0054] FIG. 8 illustrates an example of the method of multiplexing
the synchronization signal according to the present invention. In
this drawing, seven OFDM symbols constitute one slot and two slots
constitute one subframe (14 OFDM symbols). FIG. 8 illustrates an
example in which the PSS/SSS is allocated in the leading OFDM
symbol of the subframe #N.sub.SS in the ULB-CC. #N.sub.SS indicates
the first downlink subframe after the carrier sense. An example in
which the PSS and the SSS are allocated to different resource
blocks is illustrated. Thus, the synchronization signal
multiplexing units 1013-1 and 1013-2 of the ULB base station
apparatus allocate the PSS to RB #X.sub.PSS to RB
#X.sub.PSS+L.sub.PSS (the number of resource blocks is L.sub.PSS+1)
and the SSS to RB #X.sub.SSS to RB #X.sub.SSS+L.sub.SSS (the number
of resource blocks is L.sub.SSS+1). Although the PDCCH is allocated
to the leading OFDM symbol in the related art, it is assumed that
the PDCCH is not allocated to the resource blocks to which the PSS
and the SSS are allocated. The control signal such as the PDCCH or
the EPDCCH, which uses only the EPDCCH in the ULB-CC may be
transmitted in only the LB-CC in which stable communication can be
performed without being influenced by the communication of another
system. Since the ULB base station apparatus allocates the PSS and
the SSS in the LB-CC as stated above and allocates the PSS and the
SSS in the ULB-CC as illustrated in FIG. 8, the ULB base station
apparatus may change the allocation of the PSS and the SSS
depending on whether a frequency band to be used for communication
is the LB-CC or the ULB-CC. The number of resource blocks to which
the PSS or the SSS is allocated may be the number of all resource
blocks (all subcarriers) capable of being used in transmission.
Alternatively, as many signals as all the resource blocks may be
generated and allocated using a Zadoff-Chu sequence. The PSS and
the SSS may not be allocated using two Zadoff-Chu sequences, or a
signal to be allocated to the k-th subcarrier may be generated
using exp(-j.pi.uk(k+1)/N). Here, the signals may be generated
using N as the number of the largest prime number equal to or less
than the number of subcarriers to which the signals are allocated
and u as a value determined based on the cell ID. The PSS or the
SSS may be allocated to a non-continuous subcarrier, or may be
allocated at an equal interval.
[0055] In a case where the PSS/SSS is transmitted as illustrated in
FIG. 8, the terminal device detects the PSS/SSS included in the
first OFDM symbol of the leading downlink subframe after the
subframe of the carrier sense by the available subframe
determination unit 210. Thus, if the PSS/SSS is not detected in the
first OFDM symbol, the terminal device determines that the control
information or the reference signal is not transmitted from the ULB
base station apparatus, and does not need to perform radio resource
management (RRM) using the reference signal of the downlink or the
blind decoding. Thus, in a case where the PSS/SSS is not included
in the first OFDM symbol of the leading downlink subframe after the
subframe of the carrier sense, since it is difficult to determine
whether or not the subframe is the available subframe until the
OFDM symbol including the PSS/SSS, the reception process is
required. In contrast, in the present embodiment, in a case where
the subframe is not the available subframe, the unnecessary
reception process may be omitted, and thus, it is possible to
achieve power saving of the terminal device.
[0056] Although it has been described in the present embodiment
that one subframe is 1 msec, the present invention is not limited
to this example, and one subframe may not be 1 msec. Although it
has been described in the present embodiment that the cycle of the
subframe of the carrier sense is the cycle of five subframes and
the cycle of ten subframes, the present invention is not limited to
this cycle, and the pattern of the subframe of the carrier sense,
the downlink, and the uplink may be repeated within a predetermined
cycle. Although it has been described in the present embodiment
that both the PSS and the SSS are allocated to the leading OFDM
symbol of the first downlink subframe after the subframe of the
carrier sense, only any one of the PSS and the SSS may be allocated
to the leading OFDM symbol of the first downlink subframe after the
subframe of the carrier sense. Although it has been described in
the present embodiment that the PSS and the SSS are allocated to
only one OFDM symbol within one subframe, the PSS and the SSS may
be allocated to two or more OFDM symbols within one subframe, and
may be allocated to, for example, the symbol #0 and the symbol #7,
or the symbol #0 and the symbol #13. In a case where the PSS and
the SSS are allocated to a plurality of OFDM symbols, the resource
block to which the PSS and the SSS are allocated may be changed for
each OFDM symbol. Although it has been described in the present
embodiment that transmission is started in the downlink subframe
after the subframe of the carrier sense, the ULB base station
apparatus may transmit request to send (RTS) or clear to send
(CTS)-to-self before the transmission of the downlink. In this
case, the network allocation vector (NAV) may be configured for the
RTS. The ULB base station apparatus may perform the transmission of
the RTS or CTS-to-self in some of the subframes of the carrier
sense.
[0057] Although it has been described in the present embodiment
that the frame structure example is illustrated as an example of
TDD in FIG. 7, the downlink subframe immediately after the
carrier-sense subframe is not used unlike the frame structure
example of FIG. 7, and the uplink subframe may be used. For
example, the structure of the subframe may be in the order of C, U,
U, U, and D, in the order of C, U, U, D, and D, or in the order of
C, U, D, D, and D. In this case, the terminal device needs to
perform carrier sense in the carrier-sense subframe, and the
terminal device may perform data transmission in the uplink
subframe in a case where it is determined that the subframe is the
available subframe as a result of the carrier sense, and may
transmit the same PSS/SSS as that of the present embodiment, the
reference signal, or an already-known signal such as a training
symbol in the first downlink subframe of the available subframe.
The present embodiment may be applied to FDD. In a case where the
ULB-CC is the CC of the downlink, Structure 2 or Structure 8 which
is the frame structure including only D and C in FIG. 7 may be
used, and the same PSS/SSS as that of the present embodiment may be
transmitted in the first downlink subframe of the available
subframe. Although one ULB-CC has been described in the present
embodiment, a plurality of ULB-CCs may be present. In this case,
the ULB base station apparatus may perform the carrier sense in
each ULB-CC, may determine whether the subframe is the available
subframe or the unavailable subframe based on the result of the
carrier sense for each ULB-CC, and may transmit the same PSS/SSS as
that of the present embodiment in the first downlink subframe of
the available subframe. The timing of the subframe of the ULB-CC of
the present embodiment may be adjusted by synchronizing the timings
of the ULB base station apparatus and the terminal device, or the
timing between the ULB base station apparatus and the terminal
device may be adjusted to the timing of the subframe of the LB-CC
of the macro base station apparatus. Although it has been described
in the present embodiment that the ULB base station apparatus
notifies that the subframe is the available subframe by
transmitting the PSS/SSS in the leading OFDM symbol of the first
downlink subframe of the available subframe in the ULB-CC, the
present invention it not limited to this example. For example, the
reference signal such as the CRS, the CSI-RS, or the DMRS may be
used instead of the PSS/SSS, a discovery reference signal (DRS) or
a positioning reference signal (PRS) may be used, or an
already-known signal such as a training symbol may be
transmitted.
[0058] As stated above, in the present embodiment, the ULB base
station apparatus determines whether or not another system uses the
ULB-CC in the subframe of the carrier sense, and transmits the
PSS/SSS in the leading OFDM symbol of the first downlink subframe
after the subframe of the carrier sense in a case where the ULB-CC
is able to be used. The terminal device may determine whether or
not the data of the ULB-CC is able to be transmitted or received in
the leading OFDM symbol of the first subframe of the downlink, and
may share information of the result of the efficient carrier sense.
As a result, in a case where the subframe is not the available
subframe, since the terminal device does not need to perform the
reception process such as blind decoding, it is possible to reduce
a calculation amount, and it is possible to achieve power
saving.
Modification Example 1 of First Embodiment
[0059] In the present modification example, structure examples of
the ULB base station apparatus and the terminal device are the same
as those of the first embodiment, and are respectively illustrated
in FIGS. 4 and 6. A structure example of the DL signal generation
unit 101 of the ULB base station apparatus is also the same as that
of the first embodiment, and is illustrated in FIG. 5. Thus, only
different processes will be described in the present modification
example, and the description of the same processes will be
omitted.
[0060] In the present modification example, the CS determination
unit 106 and the synchronization signal multiplexing units 1013-1
and 1013-2 of the ULB base station apparatus are different from
those of the first embodiment. The CS determination unit 106
determines whether or not another system uses the ULB-CC in the
subframe of the carrier sense. Here, although it has been described
in the first embodiment that the carrier sense is performed during
all the periods of the subframes of the carrier sense, the carrier
sense is performed in the OFDM symbols except for the last OFDM
symbol (symbol #13) within the subframe of the carrier sense in the
present modification example. For example, the OFDM symbols in
which the carrier sense is performed are OFDM symbols (symbols #0
to #6) of the first slot. The synchronization signal multiplexing
units 1013-1 and 1013-2 determine whether or not another system
uses the ULB-CC, and input the result thereof to the
synchronization signal generation unit 1016. The synchronization
signal generation unit 1016 generates PSS/SSS similarly to the
first embodiment, and inputs the generated signal to the
synchronization signal multiplexing units 1013-1 and 1013-2.
[0061] FIG. 9 illustrates a method of multiplexing the PSS/SSS
according to the present modification example. This drawing
illustrates an example in which the PSS/SSS is allocated to the
last OFDM symbol of the subframe #N.sub.SS2. #N.sub.SS2 indicates
the subframe of the carrier sense. An example in which the PSS and
the SSS are allocated to different resource blocks is illustrated.
Thus, the synchronization signal multiplexing units 1013-1 and
1013-2 of the ULB base station apparatus allocate the PSS to RB
#X.sub.PSS to RB #X.sub.PSS+L.sub.PSS (the number of resource
blocks is L.sub.PSS+1) and the SSS to RB #X.sub.SSS to RB
#X.sub.SSS+L.sub.SSS (the number of resource blocks is
L.sub.SSS+1). Since the ULB base station apparatus allocates the
PSS and the SSS in the LB-CC as stated above and allocates the PSS
and the SSS in the ULB-CC as illustrated in FIG. 9, the allocation
of the PSS and the SSS is changed depending on whether a frequency
band to be used for communication is the LB-CC or the ULB-CC.
[0062] In a case where the PSS/SSS is transmitted as illustrated in
FIG. 9, the terminal device detects the PSS/SSS included in the
last OFDM symbol of the subframe of the carrier sense by the
available subframe determination unit 210. Thus, if the PSS/SSS is
detected in the last OFDM symbol of the subframe of the carrier
sense, the terminal device determines that the subsequent downlink
and uplink subframes are not the available subframes, and does not
need to perform the RRM measurement using the reference signal of
the downlink or the blind decoding, the data reception of the
downlink, or the data transmission of the uplink.
[0063] Although it has been described in the present modification
example that the PSS/SSS is transmitted in the last OFDM symbol of
the subframe of the carrier sense, a time when the ULB base station
apparatus and the terminal device transmit the signal in the ULB-CC
becomes 4 subframes+1 OFDM symbol in a case where the subframe
structure example of FIG. 3 is applied. Thus, in order to reduce
the influence on the communication of another system in the ULB-CC,
a transmit power used for the transmission of the PSS/SSS may be
lowered. In this case, a transmit-power control units is included
in the wireless transmission units 102-1 and 102-2 of the ULB base
station apparatus, and the transmit-power control unit lowers the
transmit power in the OFDM symbol in which the PSS/SSS is
transmitted and transmits the transmit power in the OFDM symbol or
the subframe in which the data of the downlink or the control
signal is transmitted without lowering the transmit power. The
transmit-power control unit transmits the transmit power in the
OFDM symbol in which the PSS/SSS of the LB-CC is transmitted
without lowering the transmit power.
[0064] Although it has been described in the present modification
example that the PSS/SSS is transmitted in the subframe of the
carrier sense, the ULB base station apparatus may transmit the
PSS/SSS in some of the OFDM symbols of the downlink subframe in
addition to the transmission of the PSS/SSS in the carrier-sense
subframe. In this case, the resource blocks in which the PSS/SSS of
the subframe of the carrier sense and the downlink subframe may be
different. For example, the ULB base station apparatus may allocate
any one of the PSS and the SSS in all the resource blocks in the
subframe of the carrier sense, and may allocate the PSS or the SSS
to some of the resource blocks in the downlink subframe.
[0065] Although it has been described in the present modification
example that the cycle of the subframe of the carrier sense is the
cycle of five subframes and the cycle of ten subframes, the present
invention is not limited to this cycle, and the pattern of the
subframe of the carrier sense, the downlink, and the uplink may be
repeated within a predetermined cycle. Although it has been
described in the present modification example that both the PSS and
the SSS are allocated to the last OFDM symbol of the subframe of
the carrier sense, only any one of the PSS and the SSS may be
allocated to the last OFDM symbol of the subframe of the carrier
sense. In this case, the synchronization signal that is not
allocated to the last OFDM symbol may be allocated to the OFDM
symbol (symbol #12) which is the second to the last OFDM symbol of
the subframe of the carrier sense. Although it has been described
in the present modification example that the PSS/SSS is transmitted
in the last OFDM symbol of the subframe of the carrier sense, the
ULB base station apparatus may transmit the RTS or CTS-to-self
before the transmission of the PSS/SSS. In this case, the NAV may
be configured for the RTS. The ULB base station apparatus may
perform the transmission of the RTS or CTS-to-self in some of the
subframe of the carrier sense.
[0066] Although it has been described in the present modification
example that the frame structure example is illustrated as an
example of TDD in FIG. 7, the downlink subframe immediately after
the carrier-sense subframe is not used unlike the frame structure
example of FIG. 7, and the uplink subframe may be used. For
example, the structure of the subframe may be in the order of C, U,
U, U, and D, in the order of C, U, U, D, and D, or in the order of
C, U, D, D, and D. The present modification example may be applied
to FDD. In a case where the ULB-CC is the CC of the downlink,
Structure 2 or Structure 8 which is the frame structure including
only D and C in FIG. 7 may be used, and the same PSS/SSS as that of
the present modification example may be transmitted in the first
downlink subframe of the available subframe. Although one ULB-CC
has been described in the present modification example, a plurality
of ULB-CCs may be present. In this case, the ULB base station
apparatus may perform the carrier sense in each ULB-CC, may
determine whether the subframe is the available subframe or the
unavailable subframe based on the result of the carrier sense for
each ULB-CC, and may transmit the same PSS/SSS as that of the
present modification example in the first downlink subframe of the
available subframe. The timing of the subframe of the ULB-CC of the
present modification example may be adjusted by synchronizing the
timings of the ULB base station apparatus and the terminal device,
or the timing between the ULB base station apparatus and the
terminal device may be adjusted to the timing of the subframe of
the LB-CC of the macro base station apparatus. Although it has been
described in the present modification example that the PSS/SSS is
transmitted in the last OFDM symbol of the subframe of the carrier
sense, the present invention is not limited to this example, and an
example in which the PSS/SSS is transmitted at a timing of any one
of the subframes of the carrier sense is included in the present
invention. Although it has been described in the present
modification example that the ULB base station apparatus notifies
that the subframe is the available subframe by transmitting the
PSS/SSS in the last OFDM symbol of the subframe of the carrier
sense in the ULB-CC, the present invention is not limited to this
example. For example, the reference signal such as the CRS, the
CSI-RS, or the DMRS may be used instead of the PSS/SSS, the DRS or
the PRS may be used, or the already-known signal such as the
training symbol may be transmitted.
[0067] As mentioned above, in the present modification example, the
ULB base station apparatus determines whether or not another system
uses the ULB-CC in the subframe of the carrier sense, and transmits
the PSS/SSS in the last OFDM symbol of the subframe of the carrier
sense in a case where the ULB-CC is able to be used. The terminal
device may determine whether the data of the ULB-CC in the last
OFDM symbol of the subframe of the carrier sense is able to be
transmitted or received, and may share information of the result of
the efficient carrier sense. As a result, the terminal device may
determine whether or not the ULB-CC is able to be used before the
subframe of the downlink and does not need to perform the reception
process such as blinding decoding in a case where the subframe is
the available subframe, it is possible to reduce a calculation
amount, and it is possible to achieve power saving.
Modification Example 2 of First Embodiment
[0068] In the present modification example, structure examples of
the ULB base station apparatus and the terminal device are the same
as those of the first embodiment, and are respectively illustrated
in FIGS. 4 and 6. A structure example of the DL signal generation
unit 101 of the ULB base station apparatus is also the same as that
of the first embodiment, and is illustrated in FIG. 5. Thus, only
different processes will be described in the present modification
example, and the description of the same processes will be
omitted.
[0069] In the present modification example, the PSS/SSS is
transmitted by the same method as that of Modification Example 1 of
the first embodiment, and is allocated to the last OFDM symbol of
the subframe of the carrier sense. Here, the UL signal generation
unit 211 of the terminal device is different from that of
Modification Example 1 of the embodiment. The UL signal generation
unit 211 generates a transmit signal of the uplink based on the
information of the timing of the uplink subframe notified from the
available subframe determination unit 210. At the transmission
timing of the uplink, the uplink pilot time slot (UpPTS) included
in the special subframe is also present in addition to the uplink
subframe. Particularly, the UpPTS is used for transmitting the SRS
or the RACH.
[0070] The special subframe includes the GP, the downlink pilot
time slot (DwPTS), and the uplink pilot time slot (UpPTS). A
proportion of GP times included in the special subframe may be
changed depending on the special subframe configuration. In the
case of a normal CP in the downlink and the uplink,
T.sub.DL=6592T.sub.S, 19760T.sub.S, 21952T.sub.S, 24144T.sub.S,
26336T.sub.S, or 13168T.sub.S is designated for the DwPTS, and
T.sub.UL=2192T.sub.S or 4384T.sub.S is designated for the UpPTS.
Here, T.sub.S is a time which satisfies 1 msec=30720T.sub.S. Since
T.sub.DL of the DwPTS and T.sub.UL of the UpPTS are uniquely
determined depending on the special subframe configuration, the GP
time is determined by T.sub.GP=30720T.sub.S=T.sub.DL-T.sub.UL.
[0071] Thus, in a case where the terminal device transmits the SRS
in the UpPTS, the transmission is started after T.sub.DL+T.sub.GP
of the special subframe. Here, in the present modification example,
in a case where the ULB base station apparatus determines that
another system does not use the ULB-CC as the result of the carrier
sense, as much time as 1 OFDM symbol+4 subframes in which the
PSS/SSS is transmitted is occupied. If the ULB-CC is occupied by
the communication between the ULB base station apparatus and the
terminal device, since another system is not able to use the
ULB-CC, an occupancy time is preferably further reduced. Thus, in
the present modification example, the GP time is calculated as
T.sub.GP2=30720T.sub.S-T.sub.DL-T.sub.UL-T.sub.symb, and the
occupied time is reduced to as much time as four subframes (4 msec)
of the related art without reducing the amount of resources capable
of being used in the communication between the ULB base station
apparatus and the terminal device. Here, T.sub.symb is a time of
one OFDM symbol. In a case where the SRS is transmitted in the
UpPTS, the UL signal generation unit 211 generates the signal
transmitted after T.sub.DL+T.sub.GP2. The wireless reception unit
105 and the UL signal demodulation unit 107 of the ULB base station
apparatus perform the reception process on the assumption that the
terminal device transmits the uplink signal after
T.sub.DL+T.sub.GP2 of the special subframe.
[0072] Although it has been described in the present modification
example that when the terminal device calculates the transmission
timing of the UpPTS, the GP time is T.sub.GP2 in the ULB-CC, the
terminal device may set the transmission timing to be T.sub.GP as
in the related art when the transmission timing of the UpPTS is
calculated in the LB-CC. Thus, the terminal device may switch the
transmission timing of the UpPTS of the special subframe between
the ULB-CC and the LB-CC. Although it has been described in the
present modification example that the time of one OFDM symbol is
subtracted when the terminal device calculates T.sub.GP2, the time
which is longer than one OFDM symbol may be subtracted. For
example, the terminal device calculates the transmission timing of
the UpPTS by subtracting as much time as two OFDM symbols at the
time of the calculation of T.sub.GP2. In such a case, the ULB base
station apparatus may use any timings of the timings after the
DwPTS as the OFDM symbols in which the PSS/SSS is transmitted as
many as the GPs are reduced.
[0073] As stated above, in the present modification example, when
the terminal device calculates a transmission start timing of the
UpPTS of the special subframe, a value acquired by subtracting one
OFDM symbol from the GP times of the related art is applied. Thus,
it is possible to reduce the occupied time, that is, the total time
of the downlink subframe, the uplink subframe, and the special
subframe, to as much time as four subframes (4 msec) of the related
art by using the PSS/SSS transmitted in the last OFDM symbol of the
subframe of the carrier sense without reducing the amount of
resources capable of being used for the communication between the
ULB base station apparatus and the terminal device. It is possible
to reduce the time when another system is not able to communicate
in the ULB-CC through the communication between the ULB base
station apparatus and the terminal device, and it is possible to
efficiently use the ULB-CC.
Second Embodiment
[0074] In the second embodiment of the present invention, a method
of transmitting the ACK/NACK of the downlink transmission in a case
where the ULB base station apparatus determines whether the
subframe is the available subframe or the unavailable subframe in
the subframe of the carrier sense as in the previous embodiment and
the ULB base station apparatus transmits the PSS/SSS in a case
where the subframe is the available subframe will be described.
[0075] In the present embodiment, structure examples of the ULB
base station apparatus and the terminal device are the same as
those of the first embodiment, and are respectively illustrated in
FIGS. 4 and 6. A structure example of the DL signal generation unit
101 of the ULB base station apparatus is also the same as that of
the first embodiment, and is illustrated in FIG. 5. Thus, only
different processes will be described in the present embodiment,
and the description of the same processes will be omitted.
[0076] When the ULB base station apparatus performs the data
transmission of the downlink, resource allocation information (DL
grant) of the downlink is generated by the control signal
generation unit 1017, and is transmitted to the terminal device.
The terminal device detects the resource allocation information (DL
grant) by the control signal detection unit 209 through blind
decoding, and performs the reception process of the data based on
the resource allocation information. As a result of the reception
process of the data, ACK/NACK which is information indicating
whether or not the resource allocation information is normally
detected is generated by the UL control information generation unit
215.
[0077] FIG. 10 shows an example of the transmission of the ACK/NACK
to the downlink according to the present invention. This drawing is
an example of the correspondence of the timing when the wireless
transmission unit 213 of the terminal device transmits the control
information of the uplink including the ACK/NACK with the reception
timing of the resource allocation or the data of the downlink. For
example, in a case where the timing when the terminal device
receives the resource allocation or the data of the downlink is any
one of the subframe #1, #2, and #3 of the frame #0, the terminal
device transmits the ACK/NACK in the first uplink subframe after
four subframes from the subframe in which the resource allocation
or the data of the downlink is received. In the example of FIG. 10,
the subframe #9 of the frame #0 is available. Here, the ULB base
station apparatus determines whether the subframe is the available
subframe which is not occupied by another system or the unavailable
subframe which is occupied by another system for each subframe of
the carrier sense. Initially, in a case where the subframes #5 to
#9 of the frame #0 are the available subframes, since the subframe
#9 of the frame #0 is able to be used, the terminal device
transmits the ACK/NACK of the data received in at least one of the
subframes #1, #2, and #3 of the frame #0 in the subframe #9 of the
frame #0.
[0078] Hereinafter, a case where the subframes #5 to #9 of the
frame #0 are the unavailable subframes will be described with
reference to FIG. 11. This drawing shows an example in which
another system uses the ULB-CC in the carrier sense of the subframe
#5 of the frame #0, and the ULB base station apparatus does not
transmit the PSS/SSS. Since the PSS/SSS is not able to be detected,
the terminal device determines that the subframes #5 to #9 of the
frame #0 are the unavailable subframes, and does not transmit the
ACK/NACK in the subframe #9 of the frame #0. Here, if the terminal
device transmits the ACK/NACK in the subframe #9 of the frame #0,
the communication of the terminal device may collide with the
communication of another system, and thus, the ULB base station
apparatus lowers a probability that the ULB-CC will be able to
receive the ACK/NACK. Thus, it is difficult to achieve stable
communication in the ULB-CC.
[0079] In a case where the ULB base station apparatus determines
that the subframes #0 to #4 of the frame #1 are the available
subframes as a result of the carrier sense in the subframe #0 of
the frame #1, the ULB base station apparatus transmits the PSS/SSS.
The terminal device determines that the subframe #4 of the frame #1
is the first uplink subframe after four subframes from the subframe
in which the downlink data is received by detecting the PSS/SSS,
and transmits the ACK/NACK.
[0080] Although it has been described in the present embodiment
that the information indicating whether the subframe is the
available subframe or the unavailable subframe between the ULB base
station apparatus and the terminal device is notified in the
detection of the same PSS/SSS as that of the previous embodiment,
the present invention is not limited to this method. Thus, an
example in which the terminal device determines whether or not the
subframe is the available subframe or the unavailable subframe by
another method and the ACK/NACK is transmitted in the first
available uplink subframe after four subframes from the subframe in
which the downlink data is received except for the uplink subframe
of the unavailable subframe is included in the present invention.
The present embodiment may be applied to FDD. In a case where the
CCs of the downlink and the uplink are present in the ULB-CC, the
ACK/NACK may be transmitted in the first available subframe of the
ULB-CC of the uplink after four subframes from the subframe in
which the downlink data is received except for the uplink subframe
of the unavailable subframe. Although one ULB-CC has been described
in the present embodiment, a plurality of ULB-CCs may be present.
In this case, the transmission timing of the ACK/NACK of the
present embodiment in each ULB-CC may be applied. The timing of the
subframe of the ULB-CC of the present embodiment may be adjusted by
synchronizing the timings of the ULB base station apparatus and the
terminal device, or the timing between the ULB base station
apparatus and the terminal device may be adjusted to the timing of
the subframe of the LB-CC of the macro base station apparatus.
[0081] As stated above, in the present embodiment, the ULB base
station apparatus and the terminal device share the information
indicating whether the subframe is the available subframe or the
unavailable subframe, and the terminal device transmits the
ACK/NACK in the first uplink subframe after four subframes from the
subframe in which the downlink data is received except for the
uplink subframe of the unavailable subframe. As a result, it is
possible to avoid the collision even though another system occupies
the ULB-CC from when the downlink data is received to when the
ACK/NACK is transmitted, and spectral efficiency is improved by
suppressing a deteriorate in communication quality of the
ULB-CC.
Modification Example 1 of Second Embodiment
[0082] In the present modification example, a method of
transmitting the ACK/NACK of the downlink transmission in a case
where the ULB base station apparatus determines whether the
subframe is the available subframe or the unavailable subframe in
the subframe of the carrier sense as in the second embodiment and
the ULB base station apparatus transmits the PSS/SSS in a case
where the subframe is the available subframe will be described.
[0083] In the present modification example, structure examples of
the ULB base station apparatus and the terminal device are the same
as those of the first embodiment, and are respectively illustrated
in FIGS. 4 and 6. A structure example of the DL signal generation
unit 101 of the ULB base station apparatus is also the same as that
of the first embodiment, and is illustrated in FIG. 5. Thus, only
different processes will be described in the present modification
example, and the description of the same processes will be
omitted.
[0084] When the ULB base station apparatus performs scheduling of
the uplink, resource allocation information (UL grant) of the
uplink is generated by the control signal generation unit 1017, and
is transmitted to the terminal device. The terminal device detects
the resource allocation information (UL grant) through blind
decoding by the control signal detection unit 209, and performs the
transmission process of the data based on the resource allocation
information. As a result of the reception process of the data, the
ULB base station apparatus generates ACK/NACK which is information
indicating whether or not the resource allocation information is
normally detected by the control signal generation unit 1017. Here,
the ACK/NACK of the data of the uplink is notified over any one or
both of PDCCH/EPDCCH and a physical hybrid-ARQ indicator channel
(PHICH).
[0085] FIG. 12 shows an example of the transmission of the ACK/NACK
to the uplink according to the present invention. This drawing
shows an example of the correspondence of the timing when the
wireless transmission unit 213 of the terminal device transmits the
data of the uplink regarding the resource allocation information of
the uplink with the timing when the wireless transmission units
102-1 and 102-2 of the ULB base station apparatus transmit the
control information of the downlink including ACK/NACK with respect
to the reception timing of the data of the uplink. For example, in
a case where the timing when the terminal device receives the
resource allocation of the uplink is any one of the subframes #1,
#2, and #3 of the frame #0, the terminal device transmits the data
in the first uplink subframe after four subframes from the resource
allocation of the uplink. In the example of FIG. 12, the subframe
#9 of the frame #0 is available. Here, the ULB base station
apparatus determines whether the subframe is the available subframe
which is not occupied by another system or the unavailable subframe
which is occupied by another system for each subframe of the
carrier sense. In a case where the subframes #5 to #9 of the frame
#0 are the available subframes, since the subframe #9 of the frame
#0 is able to be used, the terminal device transmits the resource
allocation or the data of the uplink received in at least one of
the subframes #1, #2, and #3 of the frame #0 in the subframe #9 of
the frame #0. Here, in a case where the subframes #5 to #9 of the
frame #0 are the unavailable subframes, the terminal device
transmits the data in the first uplink subframe after four
subframes from the subframe in which the resource allocation of the
uplink is received except for the uplink subframe of the
unavailable subframe.
[0086] In a case where the terminal device transmits the data of
the uplink in the subframe #9 of the frame #0, the ULB base station
apparatus transmits the ACK/NACK of the data of the uplink in the
first downlink subframe after four subframes from the subframe of
the data transmission of the uplink. FIG. 12 shows a case where the
subframes #0 to #4 of the frame #1 are the available subframes, and
in this case, the ULB base station apparatus transmits the ACK/NACK
of the data of the uplink in the subframe #3 of the frame #1.
[0087] Hereinafter, a case where the subframes #0 to #4 of the
frame #1 are the unavailable subframes will be described with
reference to FIG. 13. This drawing shows an example in which
another system uses the ULB-CC in the carrier sense of the subframe
#0 of the frame #1, and the ULB base station apparatus does not
transmit the PSS/SSS. Since the PSS/SSS is not able to be detected,
the terminal device determines that the subframes #0 to #4 of the
frame #1 are the unavailable subframes, and determines that the
ACK/NACK of the data of the uplink is transmitted in the next
subframe #6 of the frame #1 at the earliest. Here, if the ULB base
station apparatus transmits the ACK/NACK in the subframe #3 of the
frame #1, the communication of the ULB base station apparatus may
collide with the communication of another system, and the terminal
device lowers a probability that the ULB-CC will be able to receive
the ACK/NACK. Thus, it is difficult to achieve stable communication
in the ULB-CC.
[0088] In a case where the ULB base station apparatus determines
that the subframes #5 to #9 of the frame #1 are the available
subframes as the result of the carrier sense in the subframe #5 of
the frame #1, the ULB base station apparatus transmits the PSS/SSS.
The ULB base station apparatus transmits the ACK/NACK of the data
of the uplink received in the subframe #9 of the frame #0 in the
subframe #6 of the frame #1. This is because the subframe #6 of the
frame #1 corresponds to the first downlink subframe after four
subframes from the subframe in which the uplink data is received.
The terminal device determines that the subframe #6 of the frame #1
is the first downlink subframe after four subframes from the
subframe in which the uplink data is transmitted by detecting the
PSS/SSS, and performs the reception process of the ACK/NACK.
[0089] Although it has been described in the present modification
example that the information indicating whether the subframe is the
available subframe or the unavailable subframe is notified between
the ULB base station apparatus and the terminal device in the
detection of the same PSS/SSS as that of the previous embodiment,
the present invention is not limited to this method. Thus, an
example in which the terminal device determines whether or not the
subframe is the available subframe or the unavailable subframe by
another method and the ACK/NACK is transmitted in the first
available downlink subframe after four subframes from the subframe
in which the uplink data is received except for the downlink
subframe of the unavailable subframe is included in the present
invention. The present modification example may be applied to FDD.
In a case where the CCs of the downlink and the uplink are present
in the ULB-CC, the ACK/NACK may be transmitted in the first
available subframe of the ULB-CC of the downlink after four
subframes from the subframe in which the uplink data is received
except for the downlink subframe of the unavailable subframe.
Although one ULB-CC has been described in the present modification
example, a plurality of ULB-CCs may be present. In this case, the
transmission timing of the ACK/NACK of the present modification
example in each ULB-CC may be applied. The timing of the subframe
of the ULB-CC of the present modification example may be adjusted
by synchronizing the timings of the ULB base station apparatus and
the terminal device, or the timing between the ULB base station
apparatus and the terminal device may be adjusted to the timing of
the subframe of the LB-CC of the macro base station apparatus. In a
case where the subframe is not the available subframe during a
predetermined period from the resource allocation information of
the uplink or the timing of the data transmission of the uplink,
the ACK/NACK of the data of the uplink may be transmitted in
different CCs (for example, LB-CCs).
[0090] As mentioned above, in the present modification example, the
ULB base station apparatus share the information indicating whether
the subframe is the available subframe or the unavailable subframe
and the terminal device, and the terminal device transmits the
ACK/NACK in the first downlink subframe after four subframes from
the subframe in which the uplink data is received except for the
downlink subframe of the unavailable subframe. As a result, it is
possible to avoid the collision even though another system occupies
the ULB-CC from when the uplink data is received to when the
ACK/NACK is transmitted, and spectral efficiency is improved by
suppressing a deteriorate in communication quality of the
ULB-CC.
Modification Example 2 of Second Embodiment
[0091] In the present modification example, a method of
transmitting the ACK/NACK of the downlink transmission in a case
where the ULB base station apparatus determines whether the
subframe is the available subframe or the unavailable subframe in
the subframe of the carrier sense as in the second embodiment and
Modification Example 1 of the second embodiment and the ULB base
station apparatus transmits the PSS/SSS in a case where the
subframe is the available subframe will be described.
[0092] In the present modification example, structure examples of
the ULB base station apparatus and the terminal device are the same
as those of the first embodiment, and are respectively illustrated
in FIGS. 4 and 6. A structure example of the DL signal generation
unit 101 of the ULB base station apparatus is also the same as that
of the first embodiment, and is illustrated in FIG. 5. Thus, only
different processes will be described in the present modification
example, and the description of the same processes will be
omitted.
[0093] When the ULB base station apparatus performs the data
transmission of the downlink, resource allocation information (DL
grant) of the downlink is generated by the control signal
generation unit 1017, and is transmitted to the terminal device.
The terminal device detects the resource allocation information (DL
grant) by the control signal detection unit 209 through blind
decoding, and performs the reception process of the data based on
the resource allocation information. As a result of the reception
process of the data, ACK/NACK which is information indicating
whether or not the resource allocation information is normally
detected is generated by the UL control information generation unit
215.
[0094] FIG. 14 shows an example of the transmission of the ACK/NACK
to the downlink according to the present invention. This drawing is
an example of the correspondence of the timing when the wireless
transmission unit 213 of the terminal device transmits the control
information of the uplink including the ACK/NACK with the reception
timing of the resource allocation or the data of the downlink. For
example, in a case where the timing when the terminal device
receives the resource allocation or the data of the downlink is any
one of the subframe #1, #2, and #3 of the frame #0, the terminal
device transmits the ACK/NACK in the first uplink subframe after
four subframes from the subframe in which the resource allocation
or the data of the downlink is received. In the example of FIG. 14,
the subframe #9 of the frame #0 is available. Here, the ULB base
station apparatus determines whether the subframe is the available
subframe which is not occupied by another system or the unavailable
subframe which is occupied by another system for each subframe of
the carrier sense. Initially, in a case where the subframes #5 to
#9 of the frame #0 are the available subframes, since the subframe
#9 of the frame #0 is able to be used, the terminal device
transmits the ACK/NACK of the data received in at least one of the
subframes #1, #2, and #3 of the frame #0 in the subframe #9 of the
frame #0.
[0095] Hereinafter, a case where the subframes #5 to #7 of the
frame #0 are the unavailable subframes as the result of the carrier
sense by the ULB base station apparatus is an operation of FIG. 14.
The ULB base station apparatus does not transmit the PSS/SSS. Thus,
since the PSS/SSS is not able to be detected, the terminal device
determines that the subframes #5 to #7 of the frame #0 are the
unavailable subframes. The ULB base station apparatus performs the
carrier sense in the previous subframe (the subframe #8 of the
frame #0) of the uplink subframe. For example, the ULB base station
apparatus performs the carrier sense in the first slot of the
subframe #8 of the frame #0. In a case where it is determined that
the subframes #8 and #9 of the frame #0 are the available subframes
as the result of the carrier sense, the ULB base station apparatus
transmits the PSS/SSS in the last OFDM symbol of the subframe #8 of
the frame #0 as illustrated in FIG. 9. The terminal device detects
the PSS/SSS in the subframe #8 of the frame #0, determines that the
subframe #9 of the frame #0 is the available subframe, and
transmits the ACK/NACK.
[0096] Although it has been described in the present modification
example that the information indicating whether the subframe is the
available subframe or the unavailable subframe is notified between
the ULB base station apparatus and the terminal device in the
detection of the same PSS/SSS as that of the previous embodiment,
the present invention is not limited to this method. That is, an
example in which the terminal device determines whether or not the
subframe is the available subframe or the unavailable subframe by
another method and the ACK/NACK is transmitted in the first uplink
subframe after four subframes from the subframe in which the
downlink data is received except for the uplink subframe of the
unavailable subframe is included in the present invention. Although
the transmission timing of the ACK/NACK of the reception of the
resource allocation or the data of the downlink has been described
in the present modification example, the present modification
example may be applied to the transmission timing of the data of
the uplink regarding the resource allocation of the uplink.
Although it has been described in the present modification example
that the ULB base station apparatus may perform the carrier sense
in the subframe #8 of the frame #0, the terminal device performs
the carrier sense in the subframe #8, and may transmit the ACK/NACK
in the subframe #9 of the frame #0 in a case where it is determined
that the subframe is the available subframe which is not occupied
by another system. Although it has been described in the present
modification example that the special subframe of the subframe #8
of the frame #0 is the subframe of the carrier sense in a case
where another system occupies the ULB-CC in the subframe #5 of the
frame #0, the special subframe may be constantly regarded as the
subframe of the carrier sense. The present modification example may
be applied to FDD. In a case where the CCs of the downlink and the
uplink are present in the ULB-CC, the terminal device may perform
the carrier sense before the subframe of the ULB-CC of the uplink
after four subframes from the subframe in which the downlink data
is received except for the uplink subframe of the unavailable
subframe. Although one ULB-CC has been described in the present
modification example, a plurality of ULB-CCs may be present. In
this case, the transmission timing of the ACK/NACK may be
determined based on the result of the carrier sense by the terminal
device in each ULB-CC as in the present modification example. The
timing of the subframe of the ULB-CC of the present modification
example may be adjusted by synchronizing the timings of the ULB
base station apparatus and the terminal device, or the timing
between the ULB base station apparatus and the terminal device may
be adjusted to the timing of the subframe of the LB-CC of the macro
base station apparatus. In a case where the terminal device
performs the carrier sense, the terminal device may perform the
carrier sense on only a frequency band used for the transmission
within all frequency bands capable of being used for the data
transmission of the ULB-CC, and the ULB base station apparatus may
perform the carrier sense on all the frequency bands capable of
being used for the data transmission of the ULB-CC.
[0097] As stated above, in the present modification example, the
ULB base station apparatus and the terminal device share the
information indicating whether the subframe is the available
subframe or the unavailable subframe, and the terminal device
transmits the ACK/NACK in the first uplink subframe after four
subframes from the subframe in which the downlink data is received
except for the uplink subframe of the unavailable subframe. As a
result, it is possible to avoid the collision even though another
system occupies the ULB-CC from when the downlink data is received
to when the ACK/NACK is transmitted, and spectral efficiency is
improved by suppressing a deteriorate in communication quality of
the ULB-CC. Even though another system occupies the ULB-CC in the
subframe of the carrier sense present before the downlink subframe,
the carrier sense is performed before the uplink subframe. As a
result, in a case where another system does not complete the
communication before the uplink subframe, since only the uplink
subframe is able to be used even though the downlink subframe is
not able to be used, a transmission occasion of the uplink is
increased, and thus, spectral efficiency is improved.
Third Embodiment
[0098] In the third embodiment of the present invention, a method
of transmitting the ACK/NACK of the downlink transmission in a case
where the ULB base station apparatus determines whether the
subframe is the available subframe or the unavailable subframe in
the subframe of the carrier sense as in the previous embodiment and
the ULB base station apparatus transmits the PSS/SSS in a case
where the subframe is the available subframe will be described.
[0099] In the present embodiment, structure examples of the ULB
base station apparatus and the terminal device are the same as
those of the first embodiment, and are respectively illustrated in
FIGS. 4 and 6. A structure example of the DL signal generation unit
101 of the ULB base station apparatus is also the same as that of
the first embodiment, and is illustrated in FIG. 5. Thus, only
different processes will be described in the present embodiment,
and the description of the same processes will be omitted.
[0100] When the ULB base station apparatus performs the data
transmission of the downlink, resource allocation information (DL
grant) of the downlink is generated by the control signal
generation unit 1017, and is transmitted to the terminal device.
The terminal device detects the resource allocation information (DL
grant) by the control signal detection unit 209 through blind
decoding, and performs the reception process of the data based on
the resource allocation information. As a result of the reception
process of the data, ACK/NACK which is information indicating
whether or not the resource allocation information is normally
detected is generated by the UL control information generation unit
215.
[0101] FIG. 15 shows an example of the transmission of the ACK/NACK
to the downlink according to the present invention. This drawing is
an example of the correspondence of the timing when the wireless
transmission unit 213 of the terminal device transmits the control
information of the uplink including the ACK/NACK with the reception
timing of the resource allocation or the data of the downlink. For
example, in a case where the timing when the terminal device
receives the resource allocation or the data of the downlink is any
one of the subframe #1, #2, and #3 of the ULB-CC, the terminal
device transmits the ACK/NACK in the first uplink subframe after
four subframes from the subframe in which the resource allocation
or the data of the downlink is received. In the example of FIG. 15,
the subframe #9 of the ULB-CC is available. Here, the ULB base
station apparatus determines whether the subframe is the subframe
(available subframe) which is not occupied by another system or the
subframe (unavailable subframe) which is occupied by another system
for each subframe of the carrier sense. Initially, in a case where
the subframes #5 to #9 of the ULB-CC are the available subframes,
since the subframe #9 of the ULB-CC is able to be used, the
terminal device transmits the ACK/NACK of the data received in at
least one of the subframes #1, #2, and #3 of the ULB-CC in the
subframe #9 of the ULB-CC.
[0102] Hereinafter, a case where the subframes #5 to #7 of the
ULB-CC are the unavailable subframes as the result of the carrier
sense by the ULB base station apparatus is an operation of FIG. 15.
This drawing shows an example in which another system uses the
ULB-CC in the carrier sense of the subframe #5 of the ULB-CC, and
the ULB base station apparatus does not transmit the PSS/SSS. Thus,
since the PSS/SSS is not able to be detected, the terminal device
determines that the subframes #5 to #9 of the ULB-CC are the
unavailable subframes, and transmits the ACK/NACK in not the
subframe #9 of the ULB-CC but the subframe #9 of the LB-CC. This is
because it is necessary to reliably transmit the ACK/NACK in the
LB-CC in a case where the ACK/NACK is not able to be transmitted in
the ULB-CC since it is important to transmit the ACK/NACK without
an error. In a case where the ACK/NACK is able to be transmitted in
both of the LB-CC and the ULB-CC, the resource of the LB-CC may be
preferentially used.
[0103] Although it has been described in the present embodiment
that the information indicating whether the subframe is the
available subframe or the unavailable subframe between the ULB base
station apparatus and the terminal device is notified in the
detection of the same PSS/SSS as that of the previous embodiment,
the present invention is not limited to this method. That is, an
example in which the terminal device determines whether or not the
subframe is the available subframe or the unavailable subframe by
another method and the ACK/NACK is transmitted in the first uplink
subframe after four subframes from the subframe in which the
downlink data is received except for the uplink subframe of the
unavailable subframe is included in the present invention. Although
the transmission timing of the ACK/NACK of the reception of the
resource allocation or the data of the downlink has been described
in the present embodiment, the present embodiment may be applied to
the transmission timing of the data of the uplink regarding the
resource allocation of the uplink. Although it has been described
in the present embodiment that the ULB base station apparatus
performs the carrier sense in the subframe #0 of the ULB-CC, the
ULB base station apparatus or the terminal device may perform the
carrier sense in the subframe #8 of the ULB-CC as in Modification
Example 2 of the second embodiment. In this case, in a case where
it is determined that the subframe is the available subframe which
is not occupied by another system, the terminal device may transmit
the ACK/NACK in the subframe #9 of the ULB-CC as the available
subframe. In the present embodiment, in a case where another system
occupies the ULB-CC in the subframe #5 of the ULB-C, even though
the special subframe of the subframe #8 of the ULB-CC is the
subframe of the carrier sense, the special subframe may be
constantly regarded as the subframe of the carrier sense. Although
it has been described in the present embodiment that both the
resource allocation of the downlink and the data transmission of
the downlink are performed in the ULB-CC, the resource allocation
of the downlink may be performed in the LB-CC and the data
transmission of the downlink may be performed in the ULB-CC.
[0104] Although it has been described in the present embodiment
that the number of LB-CCs is one, a plurality of LB-CC may be
present, and the LB-CC in which the ACK/NACK is transmitted may be
determined based on a predetermined priority level of the LB-CC and
the information of the LB-CC associated with the ULB-CC in a case
where the ACK/NACK is not able to be transmitted in the ULB-CC. The
present embodiment may be applied to FDD. In a case where the CCs
of the downlink and the uplink are present in the ULB-CC, if the
ULB-CC of the uplink is the unavailable subframe, the ACK/NACK may
be transmitted in the LB-CC of the uplink similarly to the present
embodiment.
[0105] As stated above, in the present embodiment, the ULB base
station apparatus and the terminal device share the information
indicating whether the subframe is the available subframe or the
unavailable subframe, and the terminal device transmits the
ACK/NACK in the LB-CC in a case where it is determined that the
ULB-CC is the unavailable subframe at the transmission timing of
the ACK/NACK. As a result, it is possible to avoid the collision
even though another system occupies the ULB-CC from when the
downlink data is received to when the ACK/NACK is transmitted, and
spectral efficiency is improved by suppressing a deteriorate in
communication quality of the ULB-CC. In the present embodiment, the
terminal device may transmit the ACK/NACK without a delay at the
transmission timing of the ACK/NACK by switching to the LB-CC even
though the ULB-CC is the unavailable subframe unlike the timing of
the ACK/NACK of the related art. Even though another system
occupies the ULB-CC in the subframe of the carrier sense present
before the downlink subframe, the carrier sense is performed before
the uplink subframe. As a result, in a case where another system
does not complete the communication before the uplink subframe,
since only the uplink subframe is able to be used even though the
downlink subframe is not able to be used, a transmission occasion
of the uplink is increased, and thus, spectral efficiency is
improved.
Fourth Embodiment
[0106] In the fourth embodiment of the present invention, a method
of transmitting the data of the uplink in a case where the ULB base
station apparatus determines whether the subframe is the available
subframe or the unavailable subframe in the subframe of the carrier
sense as in the previous embodiment and the ULB base station
apparatus transmits the PSS/SSS in a case where the subframe is the
available subframe will be described.
[0107] In the present embodiment, structure examples of the ULB
base station apparatus and the terminal device are the same as
those of the first embodiment, and are respectively illustrated in
FIGS. 4 and 6. A structure example of the DL signal generation unit
101 of the ULB base station apparatus is also the same as that of
the first embodiment, and is illustrated in FIG. 5. Thus, only
different processes will be described in the present embodiment,
and the description of the same processes will be omitted.
[0108] The present embodiment will be described with reference to
FIG. 12. In the present embodiment, the synchronization signal
generation unit 1016 of the ULB base station apparatus is different
from that of the first embodiment. In a case where it is determined
that the subframe is the available subframe which is not occupied
by another system in the subframe #0 of the frame #0, the CS
determination unit 106 inputs the information of the available
subframe to the synchronization signal generation unit 1016.
Although not illustrated, the synchronization signal generation
unit 1016 is notified of a buffered data amount for transmission
from a data amount management unit included in the S/P unit 1011.
The synchronization signal generation unit 1016 generates the
PSS/SSS of the synchronization signal in a case where the subframe
is the available subframe, but changes a sequence to be generated
depending on the buffered data amount. For example, when a
Zadoff-Chu sequence or a Gold sequence is generated, a route
sequence index or an initial value of a shift register is changed
depending on the buffered data amount. A threshold of the buffered
data amount for determining whether or not to change the route
sequence index or the initial value of the shift register may be
previously determined by the system. For example, PSS/SSS of a
different sequence is generated in only a case where there is not
transmission data of the downlink. Although it has been described
that the route sequence index of the sequence or the initial value
is changed, the sequence itself may be changed.
[0109] The terminal device is notified that the sequence to be used
as the PSS/SSS is previously the control information, calculates a
correlation value using the received PSS/SSS and candidate
sequences to be transmitted, and determines whether or not the
PSS/SSS is transmitted by any sequence. Here, when the terminal
device detects the sequence of the PSS/SSS used in a case where the
buffered data amount for a downlink exceeds a threshold in the ULB
base station apparatus, the terminal device performs the same
process as that of the previous embodiment. Meanwhile, in a case
where the buffered data amount for the downlink in the ULB base
station apparatus is less than the threshold, the terminal device
performs the following process.
[0110] The terminal device receives the resource allocation of the
uplink in any one of the subframes #1, #2, and #3 of the frame #0
of FIG. 12, and determines whether the subframes #5 to #9 of the
frame #0 are the available subframes using the PSS/SSS transmitted
from the ULB base station apparatus. In a case where the PSS/SSS
indicating that the subframes #5 to #9 of the frame #0 are the
available subframes is the sequence used when the buffered data
amount for the downlink exceeds the threshold in the ULB base
station apparatus, the terminal device regards the subframe #8 of
the frame #0 as the subframe of the carrier sense. In a case where
there is not data of the downlink, there is a possibility that
another system will perform the carrier sense in the subframes #6
and #7 of the frame #0 and will determine that the ULB-CC is not
used, and there is a possibility that another system will start
communication. Thus, if the terminal device does not perform the
carrier sense in the subframe #8 of the frame #0 which is present
before the uplink subframe, there is a possibility that the
communication of the terminal device will collide with the
communication of another system. Thus, in the present embodiment,
it is possible to notify the terminal device of whether or not to
perform the carrier sense using the sequence of the PSS/SSS
transmitted from the ULB base station apparatus before the uplink
subframe. The wireless reception units 202-1 and 202-2 of the
terminal device perform the carrier sense in the subframe #8 of the
frame #0, and determine whether or not to transmit the uplink data
in the subframe #9 of the frame #0 based on the result thereof. In
a case where the uplink data is not able to be transmitted in the
subframe #9 of the frame #0, the terminal device transmits the
uplink data by any one of the methods described in the previous
embodiments. The terminal device regards a sequence that is likely
to be transmitted from the ULB base station apparatus as being
previously notified or as being configured on a per ULB-CC basis,
and similarly regards the relationship between the sequence and the
buffered data amount for the downlink as being notified or as being
configured on a per ULB-CC basis.
[0111] The present embodiment may be applied to a case where the
ACK/NACK of the downlink is transmitted. For example, in FIG. 10,
the terminal device receives the data or the resource allocation of
the downlink in any one of the subframes #1 to #3 of the frame #0,
and determines whether or not the subframes #5 to #9 of the frame
#0 are the available subframes using the PSS/SSS transmitted from
the ULB base station apparatus. In a case where the PSS/SSS
indicating that the subframes #5 to #9 of the frame #0 are the
available subframes is the sequence used when the buffered data
amount for the downlink exceeds the threshold in the ULB base
station apparatus, the terminal device regards the subframe #8 of
the frame #0 as the subframe of the carrier sense. The wireless
reception units 202-1 and 202-2 of the terminal device perform the
carrier sense in the subframe #8 of the frame #0, and determine
whether or not transmit the ACK/NACK in the subframe #9 of the
frame #0 based on the result thereof. In a case where the uplink
data is not able to be transmitted in the subframe #9 of the frame
#0, the terminal device transmits the ACK/NACK by any one of the
methods described in the previous embodiments.
[0112] Although it has been described in the present embodiment
that the terminal device notifies of whether or not to perform the
carrier sense by using the sequence of the PSS/SSS before the
ACK/NACK of the data of the downlink or the data of the uplink is
transmitted, another information may be notified using the sequence
of the PSS/SSS. For example, a plurality of sequence candidates of
the PSS/SSS may be prepared, and the terminal device may notify of
the CC (ULB-CC or CC) in which this signal is transmitted by using
the sequence of the PSS/SSS in a case where there is a plurality of
ULB-CC candidates in which the ACK/NACK of the data of the downlink
or the data of the uplink is transmitted. Although it has been
described in the present embodiment that the terminal device
performs the carrier sense in a case where the PSS/SSS is the
sequence used when the buffered data amount for the downlink
exceeds the threshold in the ULB base station apparatus, the ULB
base station apparatus may perform the carrier sense. In such a
case, in a case where it is determined that the uplink subframe is
the available subframe as the result of the carrier sense, the ULB
base station apparatus notifies the terminal device by transmitting
the PSS/SSS. The transmission timing of the PSS/SSS may be any
timing of the special subframe, may be a part (last OFDM symbol) of
the OFDM symbols of the DwPTS, may be a part of the GPs, or may a
part of the OFDM symbols of the UpPTS. The present embodiment may
be applied to FDD. In a case where the CCs of the downlink and the
uplink are present in the ULB-CC, the information indicating
whether the subframe is the available subframe or the unavailable
subframe and information indicating whether or not the terminal
device needs to perform the carrier sense in the subframe before
the transmission of the ACK/NACK in the ULB-CC of the uplink may be
notified by using the sequence of the PSS/SSS transmitted from the
ULB base station apparatus. Although one ULB-CC has been described
in the present embodiment, a plurality of ULB-CCs may be present.
In this case, the transmission timing of the ACK/NACK of the
present embodiment in each ULB-CC may be applied. The timing of the
subframe of the ULB-CC of the present embodiment may be adjusted by
synchronizing the timings of the ULB base station apparatus and the
terminal device, or the timing between the ULB base station
apparatus and the terminal device may be adjusted to the timing of
the subframe of the LB-CC of the macro base station apparatus.
[0113] As stated above, in the present embodiment, the information
indicating whether or not the subframe is the available subframe or
the unavailable subframe and the information indicating whether or
not the terminal device needs to perform the carrier sense before
the uplink subframe may be notified using the sequence of the
PSS/SSS transmitted from the ULB base station apparatus. As a
result, it is possible to avoid the collision even though another
system occupies the ULB-CC during a period from the timing when the
ULB base station apparatus performs the carrier sense to the data
transmission of the uplink, and spectral efficiency is improved by
suppressing a deteriorate in communication quality in the
ULB-CC.
Modification Example 1 of Fourth Embodiment
[0114] In the present modification example, a method of
transmitting the data of the uplink in a case where the ULB base
station apparatus determines whether the subframe is the available
subframe or the unavailable subframe in the subframe of the carrier
sense as in the previous embodiment and the ULB base station
apparatus transmits the PSS/SSS in a case where the subframe is the
available subframe will be described.
[0115] In the present modification example, structure examples of
the ULB base station apparatus and the terminal device are the same
as those of the first embodiment, and are respectively illustrated
in FIGS. 4 and 6. A structure example of the DL signal generation
unit 101 of the ULB base station apparatus is also the same as that
of the first embodiment, and is illustrated in FIG. 5. Thus, only
different processes will be described in the present modification
example, and the description of the same processes will be
omitted.
[0116] The present modification example will be described with
reference to FIG. 12. In the present modification example, the S/P
unit 1011 of the ULB base station apparatus is different from that
of the first embodiment. In a case where it is determined that the
subframe is the available subframe which is not occupied by another
system in the subframe #0 of the frame #0, the CS determination
unit 106 inputs the information of the available subframe to the
S/P unit 1011. A data amount management unit included in the S/P
unit 1011 manages information of the buffered data amount for the
transmission, and inputs dummy data to the data signal generation
units 1012-1 and 1012-2 in a case where the data amount is less
than the threshold. Here, the threshold of the buffered data amount
which is used for determining whether or not to input the dummy
data may be previously determined by the system.
[0117] In a case where there is not data of the downlink, there is
a possibility that another system will perform the carrier sense in
the subframes #6 and #7 of the frame #0 and will determine that the
ULB-CC is not used, and there is a possibility that another system
will start communication. Thus, the ULB base station apparatus
transmits the dummy data so as to recognize that the communication
is performed between the ULB base station apparatus and the
terminal device even though another system performs the carrier
sense. A density of the reference signal may be increased instead
of using the dummy data.
[0118] Although the data transmission of the uplink of FIG. 12 has
been described in the present modification example, the present
invention may be applied up to the transmission timing of the
ACK/NACK of the downlink data of FIG. 10. The ULB base station
apparatus may transmit the RTS or CTS-to-self instead of
transmitting the dummy data, and may configure the NAV.
[0119] Although one ULB-CC has been described in the present
embodiment, a plurality of ULB-CCs may be present. In this case,
the transmission timing of the ACK/NACK of the present embodiment
in each ULB-CC may be applied. The timing of the subframe of the
ULB-CC of the present embodiment may be adjusted by synchronizing
the timings of the ULB base station apparatus and the terminal
device, or the timing between the ULB base station apparatus and
the terminal device may be adjusted to the timing of the subframe
of the LB-CC of the macro base station apparatus.
[0120] As mentioned above, in the present modification example, the
ULB base station apparatus can reserve the resources from the
resource allocation of the uplink to the transmission of the
uplink. As a result, since another system is not able to occupy the
ULB-CC during a period from the timing when the ULB base station
apparatus performs the carrier sense to the data transmission of
the uplink, it is possible to avoid the collision, and spectral
efficiency is improved by suppressing a deteriorate in
communication quality in the ULB-CC.
[0121] The programs operated in the base station apparatus and the
terminal devices according to the present invention may be programs
(programs causing a computer to function) for controlling a CPU
such that the functions of the above-described embodiments
according to the present invention are realized. The information
items treated by these apparatuses and devices are temporally
accumulated in a RAM during the processing, are stored in various
ROMs or HDDs, are read by the CPU if necessary, and are modified
and rewritten. Here, as a recording medium that stores the
programs, any one of a semiconductor medium (for example, ROM or
non-volatile memory card), an optical recording medium (for
example, DVD, MO, MD, CD, and BD), a magnetic recording medium (for
example, magnetic tape and flexible disk) may be used. The
functions of the present invention may be realized by performing
the process in cooperation with other application programs or an
operating system based on the instruction of the program, in
addition to realizing the functions of the aforementioned
embodiments by executing the loaded program.
[0122] When the programs are distributed on the market, the
programs may be distributed by being stored in a portable recording
medium, or may be transmitted to a server computer connected via a
network such as the Internet. In this case, a storage device of the
server computer may also be included in the present invention. Some
or all of the base station apparatuses and the terminal devices of
the above-described embodiments may be typically realized as large
scale integration (LSI) which is integrated circuit. The functional
blocks of the base station apparatuses and the terminal devices may
be separately realized as chips, or some or all thereof may be
integrated and realized as chips. A method for achieving the
integrated circuit is not limited to the LSI, but may be realized
by a dedicated circuit or a general-purpose processor. In a case
where the respective functional blocks are realized as the
integrated circuits, an integrated circuit control unit for
controlling these circuits is provided.
[0123] A method for achieving the integrated circuit is not limited
to the LSI, but may be realized by a dedicated circuit or a
general-purpose processor. In a case where a technology of
realizing the devices or functional blocks as the integrated
circuit has appeared instead of the LSI due to the advance of
semiconductor technology, it is possible to use an integrated
circuit produced using this technology.
[0124] The present invention is not limited to the above-described
embodiments. The terminal device according to the present invention
is not limited to the application to a mobile station apparatus,
and may be applied to stationary or non-movable electronic devices
which are installed indoors or outdoors, such as AV devices,
kitchen devices, cleaning and washing machines, air conditioners,
office devices, vending machines, and other home appliances.
[0125] The embodiments of the present invention have been described
with reference to the drawings. However, the detailed structure is
not limited to the above-described embodiments, and the present
invention also includes a change in the design within the gist of
the invention. The present invention may be variously changed
without departing from the claims, and embodiments acquired by
appropriately combining technical means disclosed in different
embodiments are included in the technical range of the present
invention. The elements described in the respective embodiments and
structures acquired by replacing the elements that exhibit the same
effects are included therein.
[0126] The present international application claims priority based
on Japanese Patent Application No. 2014-137378 filed on Jul. 3,
2014, and the entire content of Japanese Patent Application No.
2014-137378 is incorporated by reference in the present
international application.
REFERENCE SIGNS LIST
[0127] 10 MACRO BASE STATION APPARATUS [0128] 11 ULB BASE STATION
APPARATUS [0129] 21, 22 TERMINAL DEVICE [0130] 101 DL SIGNAL
GENERATION UNIT [0131] 102-1, 102-2 WIRELESS TRANSMISSION UNIT
[0132] 103-1, 103-2 TRANSMIT ANTENNA [0133] 104 RECEIVE ANTENNA
[0134] 105 WIRELESS RECEPTION UNIT [0135] 106 CS DETERMINATION UNIT
[0136] 107 UL SIGNAL DEMODULATION UNIT [0137] 1011 S/P UNIT [0138]
1012-1, 1012-2 DATA SIGNAL GENERATION UNIT [0139] 1013-1, 1013-2
SYNCHRONIZATION SIGNAL MULTIPLEXING UNIT [0140] 1014-1, 1014-2
CONTROL SIGNAL MULTIPLEXING UNIT [0141] 1015-1, 1015-2 REFERENCE
SIGNAL MULTIPLEXING UNIT [0142] 1016-1, 1016-2 SYNCHRONIZATION
SIGNAL GENERATION UNIT [0143] 1017-1, 1017-2 CONTROL SIGNAL
GENERATION UNIT [0144] 1018-1, 1018-2 REFERENCE SIGNAL GENERATION
UNIT [0145] 1019-1, 1019-2 IFFT UNIT [0146] 201-1, 201-2 RECEIVE
ANTENNA [0147] 202-1, 202-2 WIRELESS RECEPTION UNIT [0148] 203-1,
203-2 FFT UNIT [0149] 205-1, 205-2 CONTROL SIGNAL DEMULTIPLEXING
UNIT [0150] 206-1, 206-2 REFERENCE SIGNAL DEMULTIPLEXING UNIT
[0151] 207 RECEPTION SIGNAL DETECTION UNIT [0152] 208 CHANNEL
ESTIMATION UNIT [0153] 209 CONTROL SIGNAL DETECTION UNIT [0154] 210
AVAILABLE SUBFRAME DETERMINATION UNIT [0155] 211 UL SIGNAL
GENERATION UNIT [0156] 212 UL CONTROL INFORMATION MULTIPLEXING UNIT
[0157] 213 WIRELESS TRANSMISSION UNIT [0158] 214 TRANSMIT ANTENNA
[0159] 215 UL CONTROL INFORMATION GENERATION UNIT
* * * * *